1. Technical Field
The disclosure relates to a solid state image sensor generating an imaging signal by photoelectric conversion of light and an endoscope and an endoscope system acquiring the imaging signal generated by the solid state image sensor.
2. Related Art
In the related art, endoscopes are widely used for various examinations in medical fields and industrial fields. Among them, in medical endoscopes, a flexible insertion unit having an elongated shape where an imaging element including a plurality of pixels is provided to a distal end thereof is inserted into a body cavity of an subject such as a patient, and thus, an in-vivo image of an inner portion of the body cavity can be acquired without cutting the subject. Therefore, small burden is exerted on the subject, and the spread is proceeding.
As imaging modes of the endoscope, there are widely known a white light imaging (WLI) mode using white illumination light and a narrow-band imaging (NBI) mode using illumination light (narrow-band illumination light) including light of two narrow bands included in each of wavelength bands of, for example, blue light and green light. Among them, in the narrow-band imaging mode, an image for highlighting capillaries existing on a biological mucosal surface (biological surface), mucosal fine patterns, and the like can be obtained. According to the narrow-band imaging mode, a lesion on the biological mucosal surface can be more accurately identified. In the endoscope, it is preferable that observation be performed by switching between the white light imaging mode and the narrow-band imaging mode.
In the above-described imaging mode, since a color image is generated to be displayed, in order to acquire an image captured by a single plate with a solid state image sensor, in general, color filters arrayed for respective pixels using a filter array called a Bayer array as one unit are provided on a light receiving plane of the solid state image sensor (for example, refer to Japanese Laid-open Patent Publication No. 2005-334257). In this case, each pixel receives light of a wavelength band passing through the filter and generates an electric signal of a color component according to the light of the wavelength band. For this reason, in a process of generating the color image, an interpolation process is performed to interpolate a signal value of a missing color component which does not pass through the filter corresponding to each pixel.
Japanese Laid-open Patent Publication No. 2007-54113 discloses an array of color filters for performing observation appropriate to the narrow-band imaging mode. According to Japanese Laid-open Patent Publication No. 2007-54113, since one of two filters transmitting light of a green wavelength band in a Bayer array is replaced with a filter transmitting light of a blue wavelength band, the image obtained in the narrow-band imaging mode can be clarified.